If nothing is causing these signs to show up, example: If you've eaten something different, habits have changed, stressed out more; Then yes, I would assume you are pregnant.
If the spotting showed up when your period is supposed to show up, if you know when your period is supposed to come around, take a test. If it was early, wait a week or two, and take a test.
Do you think you might be pregnant? If so, take a test.